MADEIRAN GROUP. 135 



in being altogether more solid and robust, and in its umbilicus 

 being relatively a trifle smaller. In addition too to its spire 

 being more exserted (or less obtuse), it possesses an extra whorl 

 (namely 7, instead of 6); the granulations of its upper portion 

 are slightly coarser and rougher ; its basal volution is more sud- 

 denly deflected in front ; and it is usually of a rather whiter tint 

 beneath, but of a somewhat deeper brown above, the region 

 towards the aperture, however, being gradually diluted in hue, 

 or subflavescent. Like the H. leptosticta, it will generally be 

 seen, when accurately inspected, to possess obscure traces of an 

 obsolete band immediately below the dorsal line (or the place 

 which, had it been carinated, would have been occupied by the 

 keel). 



The H. micromphala is essentially a Desertan species, on 

 the whole three islands of which I have myself met with it. It 

 was first found by Mr. Leacock, in June 1848 ; and it has sub- 

 sequently been obtained by both Mr. Lowe and the Baron Paiva, 

 on various occasions. On the summit of the Southern Deserta 

 (or Bugio) it is not uncommon in a subfossil state. 



Helix dealbata, 



Helix dealbata, Lowe, Cambr. Phil. S. Trans, iv. 48. t. 5. 



f. 21 (1831) 



Pfeiff., Mon. Hel. i. 166 (1848) 



Lowe, Proc. Zool. Soc. Lond. 196 (1854) 



Alb., Mai. Mad. 31. t. 7. f. 25-28 (1854) 



Paiva, Mon. Moll. Mad. 54 (1867) 



Habitat Portum Sanctum (insulasque parvas adjacentes) ; 

 vulgaris. 



The H. dealbata and fictilis are peculiar to Porto Santo 

 and the adjacent rocks ; and although, in a general sense, suffi- 

 ciently distinct inter se to be easily separated, intermediate 

 states (in outline, sculpture, and size) do nevertheless occur 

 which so far connect the two as to render it at times not quite 

 apparent to which of the forms they should be assigned. Still, 

 as they have been universally acknowledged hitherto, and are in 

 most instances at once recognisable, I will not do more than 

 record a passing doubt as to the possibility of their being in 

 reality but well-marked phases of a single type. 1 



1 Even Mr. Lowe seems to have had the difficulty in the precise identifica- 

 tion of some of these occasional intermediate forms practically brought home 

 to him; for the 'var. /8. kevis ' of his original H. dealbata (in 1831) he subse- 

 quently treated (both in 1851 and 1852) as a var. .' of the fictilis. But two 

 years afterwards he referred it back again (vide 'Proc. Zool.' Soc. Lond.' 196; 

 1854) to the dealbata, with which, on further consideration, he appears to 

 have thought that it would, after all, be better associated. 



